Environmental Risk Assessment as a Tool to Enhance Maritime Spatial Planning in the Mediterranean Sea: The Case Study of the Gulf of La Spezia (North-Western Italy)

Maritime Spatial Planning is a pivotal tool for the sustainable development of coastal areas and the implementation of the blue economy. It requires a spatially explicit environmental risk assessment, including risk identification, analysis and evaluation, following the principles of Ecosystem-Based Management. This study aims to test an Environmental Risk Assessment approach using the InVEST Habitat Risk Assessment model to enhance Maritime Spatial Planning in the northern Mediterranean Sea. The model requires spatial data representing the distribution of habitats and stressors, and user-provided tabular data describing their interactions; it then produces quantitative, spatially explicit risk estimates, useful to prioritize actions for risk mitigation. The approach was applied in the Gulf of La Spezia (Italy), one of the most critical areas for Maritime Spatial Planning implementation in the Northwestern Mediterranean. Indeed, the gulf is a hotspot for marine biodiversity, hosting three Marine Protected Areas with valuable habitats like the Mediterranean coral Cladocora caespitosa, Posidonia oceanica meadows, Cymodocea nodosa seagrass beds, and animal forests. Nonetheless, several economically important human activities are located in the area, such as shipping, shipbuilding industries, Navy bases and arsenals, aquaculture plants, fishing and diving centres, as well as ports and other nautical facilities. Results show that risk is concentrated near coastlines (within the first 250 metres from the coast) and around islands, reflecting the spatial overlap between susceptible habitats and anthropogenic activities. The major stressors are activities/infrastructures connected with nautical tourism and coastal urbanization, such as leisure boat anchorage areas, sewage pipelines, tourist ports, and nautical facilities. A set of management actions is discussed for risk reduction, including stricter local enforcement of existing regulations and the installation of eco-friendly moorings. The proposed approach has proven to be suitable to understand habitat vulnerabilities and criticalities in a Mediterranean marine test site, providing relevant evidence-based information that could eventually steer stakeholders in defining actions for risk management. Its transparency and ease of replication make it a sound choice to build ecosystem-based knowledge, which is essential for balancing socio-economic targets with the preservation of biodiversity, ecosystem functions, and ecosystem services.